Plate Tectonics

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Plate Tectonics by Mind Map: Plate Tectonics

1. Magnetic field

1.1. Invisible lines of force that varies with distance from the equator

1.2. Paleomagnetism: study of magnetic rocks and sediments to record the history of magnetic field

2. Why study it?

2.1. Explain geographic distribution of geologic hazards such as earthquake and volcanic eruptions

2.2. Explain the distribution of geologic resources

3. Early Theories

3.1. Early 1800s: Earth was made from molten mass

3.1.1. Did not explain rift valleys

3.2. 1885: Edward Suess → India, Africa, Australia, and South America were connected

3.3. 1915: Alfred Wegener → Pangea (all landmasses were once one supercontinent)

3.4. 1960s: Plate tectonics

3.4.1. Lithosphere (both oceanic and continental) is broken into plates

4. Continental Drift

4.1. The continents were once joined together. Evidenced by:

4.1.1. Continental Fit

4.1.1.1. The continents fit together when joined along their continental slope (ignoring slight reconfigurations due to erosions)

4.1.2. Similarity of rock sequences and mountain ranges

4.1.3. Distribution of glacial features

4.1.4. Distribution of fossil land animals and plants

5. Supercontinent Cycle

5.1. Plate movements that led to the assembly of Pangea (late Paleozonic era)

6. Plate Boundaries

6.1. Divergent

6.1.1. Upwelling magma causes uplift stretching and fracturing of the overlying continental crust. Ex: East African rift

6.2. Convergent

6.2.1. Plates collide and the leading edge of one plate is subducted beneath the margin of the other plate. The

6.2.1.1. The subducted plate becomes magma, and will rise to form volcanes

6.3. Transform

6.3.1. Plates slide laterally past each other (mostly oceanic crust

7. Plate movements and motion

7.1. Determined by

7.1.1. Magnetic anomalies

7.1.1.1. Plate movement average rate = Age of a magnetic anomaly in oceanic crust / the distance between that anomaly and the present mid- ocean ridge

7.1.2. Matching crustal features and anomalies

7.1.3. Direct measurement

7.1.4. Hot spots

7.1.4.1. A fixed reference point to determine motion of plate. Ex: Under Hawaiian Islands

7.2. The uneven distribution of heat in Earth drives the plate movements by convection

7.2.1. Models of thermal convection

7.2.1.1. Restricted to asthenosphere

7.2.1.2. Entire mantle

7.2.1.3. Two-tiered convection-cell

8. Polar Wandering

8.1. Position of magnetic poles have shifted over time